The invention concerns an analytical test element comprising an absorbent material with a sample application and detection zone and a blister filled with liquid on a support. In addition the invention concerns a process for the production of such an analytical test element and a method for determining an analyte with such an analytical test element.
So-called carrier-bound tests are often used for the qualitative or quantitative analytical determination of sample components. In these the reagents are embedded in appropriate layers of an analytical test element which is contacted with the sample. As a rule the detection reactions proceed in a liquid phase. This liquid is usually derived from the sample itself in the case of liquid samples or the liquid is applied to the sample on the analytical test element. The reaction of sample and reagents then leads to a detectable signal, in particular a colour transition which can be analysed visually or with the aid of an instrument, usually by reflection photometry. Electrochemical methods of detection are now also possible on analytical test elements.
Analytical test elements are often in the form of test strips which are essentially composed of an elongate carrier i.e. a support layer for example made of plastic material and detection layers mounted thereon as test zones. However, analytical test elements are also known that are in the form of small quadratic or rectangular plates.
Analytical test elements of the type mentioned above are for example known from the European Patent document 0 279 574. The analytical test element described in this patent contains an absorbent layer with a sample application and detection zone as well as a blister filled with liquid made of a rupturable specially shaped material within a liquid-impermeable housing. The blister is formed from a stiff but nevertheless deformable plastic in such a way that it has a dome-shaped surface in which one or several pointed, rigid infolds pointing inwards are formed. When external pressure is applied to these pointed infolds the opposite blister wall is pierced and the liquid present in the blister escapes. On contact with the absorbent layer the liquid is taken up by this layer and spreads out there by capillary force. The sample material to be examined is then reacted in the liquid with the detection reagents. The special shape of the blister is relatively complicated to manufacture. Furthermore the overall manufacture of such blisters filled with liquid can only be carried out in a discontinuous manner because firstly it must be shaped by means of injection moulding or a deep-drawing process, subsequently filled with liquid and finally sealed liquid-tight with a piercable foil.